Management of stenosis of the trachea and bronchi, including laryngotracheal and subglottic stenosis, is one of the most challenging problems for the head and neck surgeon. Subglottic stenosis is a congenital or acquired narrowing of the subglottic airway. In the early twentieth century subglottic stenosis was rare, and most cases occurred in adults. In the 1960's the incidence of acquired subglottic stenosis began to dramatically increase in the neonatal population, most likely the result of increased survival of low-birth-weight infants and the increased use of intubation in this population. In addition, long term intubation has become an accepted alternative to tracheotomy, leading to more and more incidences of tracheal stenosis. Accordingly, the management of this condition has undergone a revolution, and reconstructive surgery efforts have been directed towards this population.
Most patients with stenosis of the airway are referred to and are treated at large academic centers by physicians specially trained in this area. There is a wide range of presentation of subglottic stenosis with similarities and differences in the pediatric age group compared to adults. If the stenosis is severe and congenital, the patient will show signs of airway distress at birth. More commonly, the pediatric patient with subglottic stenosis is a neonate in the intensive care unit who has failed extubation, usually multiple times. Occasionally patients will present in clinic with a tracheotomy and the report of some airway obstruction. Infants with mild subglottic stenosis may present with recurrent croup-like illnesses and poor feeding. Adults usually have a history of prior intubation with symptoms of progressive shortness of breath and noisy breathing.
Airway balloon dilation has been shown to be a safe and effective palliative procedure for treatment of mild congenital and acquired stenosis of the trachea and bronchi. Dilation of luminal human anatomy to treat stenoses can be dated back to the 16th Century with esophageal “bougie” dilation. Specific medical applications of luminal balloon dilation range from alimentary canal and airway dilation to dilation of the vasculature. Airway dilation dates back over 100 years ago with the invention and subsequent use of the first beveled rigid bronchoscopes for stricture management. The use of balloons to dilate airway strictures emerged in the mid-1980's with reports describing more specific utility of this procedure exclusively and in combination with other treatment modalities for airway stenosis. It was not until the early 1990's that the first balloon dilation involving flexible bronchoscopy was described.
Airway balloon dilation can be used to quickly re-establish tracheal or bronchial luminal patency to restore airflow in a way that doesn't cause excessive trauma to the patient. According to Poiseuille's Law, an increase in a tube's radius (such as the trachea or bronchus) can increase airflow by a power of 4 (airflow=radius of the tube4). That is, very small increases in the luminal diameter of the airway can lead to large increases in airflow through the lungs. Literature has reported the use of balloon dilation for the treatment of benign strictures of the airway. Fibrotic strictures, such as those secondary to tuberculosis, long-term endotracheal or tracheostomy tube placement, berylliosis, Wegener's granulomatosis, or sarcoidosis have been shown to be treatable with airway balloon dilation therapy with general success. Additionally, balloon dilation has been useful in treating strictures secondary to major surgical interventions such as lung transplantation, sleeve resection, bronchial re-implantation, and lobectomy. For the purpose of treating strictures secondary to malignant obstruction, dilation therapy can be used alone or in combination with other techniques such as surgical resection, cryotherapy, laser therapy, and stent placement, depending on the desired outcome for the patient.
Treatment with airway dilation can involve the clinician inserting increasingly larger tubes into the airway (e.g. endotracheal tubes or cat-tail (bougie) dilators), which creates significant shear forces on the airway mucosa. Although safe when performed by a skilled clinician, such a procedure sometimes induces unwanted trauma to the airway in the form of deep lacerations and hemoptysis. Further, current dilation practices do not permit dilation of a tracheal stenosis that is distal to a narrowing of the proximal airway (i.e. a mild subglottic stenosis).
Current airway balloon dilation procedures are typically carried out using angioplasty balloons; however, several limitations to the use of angioplasty balloons become evident when used on the airway. For example, it may be difficult to adequately ventilate the patient during the dilation period, since the typical angioplasty balloon does not include a connection to an oxygen source. Further, the shape of the angioplasty balloon may predispose the balloon to slide out of place during dilation, or the balloon may be limited to the amount of pressure that can be applied before the balloon bursts. Also, the typical angioplasty balloon can usually stretch the airway lumen but not permanently dilate it. Other factors associated with failure of airway balloon dilation include previous attempts at endoscopic repair, circumferential scarring, and loss of cartilaginous support.
In light of the foregoing, it would be advantageous to provide a balloon dilator for the airway of a patient that is able to allow ventilation of the patient during balloon inflation. It would also be helpful to provide an airway balloon dilator that can provide increased inflation pressures during balloon dilation of the airway without balloon rupture. Further, it would be beneficial to provide a balloon that will not slip out of place in the patient's airway during balloon inflation. Finally, it is desirable to provide an airway balloon dilator that is capable of controlled cutting of scar tissue.